Track circuit



Patented Aug. 4, 1936 uNi'rE srArss ATENT OFFICE TRACK CIRCUIT Application October 17, 1934, Serial No. 748,675

16 Claims,

My invention relates to railway track circuit apparatus, and more specifically to apparatus for increasing the shunting sensitivity of track circuits.

I will describe several forms of track circuit apparatus embodying my invention, and. will then point out the novel features thereof in claims.

' Fig. 1 of the accompanying drawing is a diagrammatic view showing one form of apparatus embodying my invention. Figs. 2 and 3 are fragmentary diagrammatic viewsillustrating modifled. forms of a portion of the apparatus shown in Fig. 1, and. each also embodying my invention.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Fig. 1, the reference characters l and 2 designate the rails of a section of railway track electrically isolated from the adjoining portions of the track by insulated joints Ill. At one end of the section is a transformer T and a reactor R. The primary 3 of the transformer T is connected to a suitable source of alternating current, the terminals of which are designated X and O. The secondary 4 of the transformer T is connected across the rails to supply current, through the windings 6 and. 1 of the reactor R, to a track relay P which is connected across the rails at the other end of the section. The winding 8 of the reactor R is connected to the direct current terminals of a rectifier Q, the alternating current terminals of which are connected to the rails in multiple with the track relay P.

The reactor R comprises a continuous magnetic core 5 having a center leg and two outer legs. The outer legs are provided with the windings 6 and I so connected that the fluxes induced in the core 5 by their energization is additive; therefore, no current is induced in the winding 8 which is wound about the center leg. The direct current, from the rectifier Q, flowing in winding 8'serves to create a flux which varies the permeability of the magnetic core 5 whereby the reactance of the windings 6 and 1 can be made variable. 7

When the track is shunted by a train, the currentsupplied to the rectifier Q and the track relay P is reduced; so that the direct current flowing in the winding 8 is reduced, and this causes a relatively large increase in the reactance of windings 6 and l. The increased reactance in windings 6 and i still further reduces the current available at the rectifier Q and the track. relay P. v H

Thus it will be seen that I have provided a means, when the track is shuntedffor causing an increase in the impedence between the transformer T and the rails, and, consequently, a relatively larger reduction in the amount of cur- 7, rent flowing through the winding of track relay P, than would obtain if the usual current limiting reactor were used.

Since the shunting sensitivity of a track circuit is largely determined by the amount of 10 impedance in series with the source of track circuit current, the marked advantage of the apparatus shown in Fig. 1 is obvious. A high impedance in series with the .source of track circuit current causes a relatively large potential 1.; drop when the track is occupied, so that the voltage across the track relay is greatly reduced, whereupon positive release of the relay is assured.

From the foregoing explanation, it is clear that a train shunt of much higher resistance 2n will be effective in causing relay P to release if the reactor R is used, than if the usual type of reactor is employed.

If it is desired to regulate the flow of current through the rectifier Q, a transformer TA having a variable secondary as illustrated in Fig. 2, or a variable resistor S as illustrated in Fig. 3, may be used. Otherwise, the apparatus shown. in Figs. 2 and 3 is the same as that shown'in Fig. 1. 3,0

Although I have herein shown and described only a few forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without de- 35 parting from the spirit and scope of my invention.

Having thus described my invention, what I claim is: 1. In combination, a section of railway track, a source of track circuit current connected across the rails of said section, a track relay receiving current from the rails of said section, a reactor having a main winding connected between said source and one rail of said section, 4,; an auxiliary winding for said reactorfor setting up in the reactor a fluxfor regulating-the current flowing though said main winding, and means including a rectifier connected across the rails of said section for supplying a variable 50 amount of current to said auxiliary winding to govern the amount of current received by said relay in response to; traflic conditions in said section. V

2. In combination, a'section of. railway track;

a track circuit for said section including the two rails of said track, a source of current connected across said rails at one end of the section, a track relay connected across the rails at the other end of the section, and a reactor having a main winding connected between said source and one rail of said section; and an auxiliary winding for said reactor receiving current from the rails of said section for setting up in said reactor a flux for regulating the current flowing through said main winding to improve the shunting sensitivity of said track circuit when the section is occupied by a train.

3. In combination, a section of railway track, a source of track circuit current connected across the rails of said section, a track relay receiving current from the rails of said section, a reactor having a main winding connected between said source and one rail of said section, an auxiliary winding for said reactor for setting up in the reactor a fiux for regulating the current flowing through said main winding, means including a rectifier for supp-lying current to said auxiliary winding, and means including a transformer having its primary connected across the rails of said section for supplying a variable amount of current to said rectifier in response to traiiic conditions in the section for governing the amount of current received by said relay.

4. In combination, a section otrailway track, a source of track circuit current connected across the rails of said section, a track relay receiving current from the rails of said section, a reactor having a main winding connected between said source and one rail of said section, an auxiliary winding for said reactor for setting up in the reactor a flux for regulating the current flowing through said main winding, means controlled by traflic conditions in said section and including a rectifier receivingcurrent from the rails of said section for supplying a variable amount of current to said auxiliary winding according as said section is occupied or unoccupied, thereby governing the amount of current received by said relay, and a variable resistor for limiting the amount of current received by said rectifier.

5. In combination, a section of railway track, a source of track circuit current connected across the rails of said section, a track relay receiving current from the rails of said section, a reactor having a main winding connected between said source and one rail of said section and an auxiliary winding for setting up in the reactor a fiux for regulating the current flowing through said main winding, means controlled by trafic conditions in said section and including a rectifier receiving current from the rails of said section for supplying a variable amount of current to said auxiliary winding according as said section is occupied or unoccupied, thereby governing the amount of current received by said relay, and means not responsive to traiiic conditions for regulating the amount of current received by said rectifier.

6. In combination, a section of railway track, a source of alternating track circuit current connected across the rails of said section, a track relay receiving current from the rails of said section, a reactor having a main winding connected between said source and one rail of said section, an auxiliary winding for said reactor serving when energized by direct current to set up in the reactor a flux for regulating the current flowing through said main winding, and means controlled by trafiic conditions in said section and including a rectifier receiving current from the rails of said section for supplying a variable amount of direct current to said auxiliary winding to improve the shunting sensitivity of said relay when said section is occupied by a train.

7. In combination, a section of railway track, a source of track circuit current connected across the rails of said section, a track relay receiving current from the rails of said section, a threelegged reactor having a main winding comprising a coil on each outer leg connected in series said 'main winding being interposed between said source and one rail of said section, an auxiliary winding for said reactor comprising a coil on the third leg thereof for setting up in the reactor a flux for regulating the current flowing through the main Winding, and means responsive to trafiic conditions in said section for supplying a Variable amount of current to said auxiliary winding 'to govern the amount of current received by said relay in accordance with the occupied or unoccupied condition of said section.

8. In combination, a section of railway track, a source of track circuit current connected across the rails of said section, a track relay receiving current from the rails of said section, a three-legged reactor having a main winding comprising a coil on each outer leg so connected that no flux is set up in the third leg from the main winding, said main winding being interposed between said source and one rail of said section, an auxiliary winding comprising a coil on the third leg for setting up in the reactor a flux for regulating the current flowing through the. main Winding, and means responsive to trafiic conditions in said section for supplying a variable amount of current to said auxiliary winding to govern the amount of current received by said relay in accordance with the occupied or unoccupied condition of said section.

9. In combination, a section of railway track. a source of track circuit 7 current connected across the rails of said section, a track relay receiving current from the rails of said section, a three-legged reactor having a main winding comprising a coil on each outer leg soconnected that no flux is set up in the third leg from the main Winding, said main Winding being interposed between said source and one railof said section, an auxiliary Winding comprisinga coil on the third leg for setting up in the reactor a flux for regulating the current flowing through the main winding, and means including a rectifier connected across the rails of said section for supplying a variable amount of current to said auxiliary winding to govern the amount of current received by said relay in response to trafiic conditions insaid section.

10. In combination with a section of railway track, a source of periodic current, means for connecting said source across the traffic rails of the section including a first winding of a reactor having a magnetizable core, a trafiic governing relay, means adapted to receive periodic current from the traflic rails for energizing said relay, other means adapted to receive periodic current from the traffic rails of the section including an asymmetric unit for converting the periodic current into unidirec-.

flux in the core of the reactor in accordance with the occupied or unoccupied condition of said section.

11. In combination with a section of railway track, a source of periodic current, means for connecting said source across the traific rails of the section including a first winding of a reactor having a magnetizable core, a trafiic governing relay, means adapted toreceive periodic current from the trafiic rails for energizing said relay, other means adapted to receive periodic current from the traflic rails of the section including an asymmetric unit for converting the periodic current into unidirectional current, and means energized from the output of said asymmetric unit including a second winding of the reactor and controlled by traffic conditions in said section for varying the permeability of the core of said reactor to control the periodic current supplied to the traffic rails in accordance with the occupied or unoccupied condition of said section.

12. In combination with a section of railway track, a source of periodic current, means for connecting said source across the traffic rails of the section including a first winding of a reactor having a magnetizable core, a traffic governing relay, means adapted to receive periodic current from the trafiic rails for energizing said relay, other means adapted to receive periodic current from the trafiic rails of the section including an asymmetric unit for converting the periodic current into unidirectional current, and means connected with the output of said asymmetric unit including a second Winding of the reactor for governing the flux in the core of the reactor whereby the reactance of said first winding is controlled in accordance with the presence or absence of a train in said section.

13. In combination with a section of railway track, a source of periodic current, means for connecting said source across the traflic rails of the section including a first winding of a reactor having a magnetizable core, a second winding mounted on the core of said reactor,

circuit means including a source of direct current for energizing said second winding to create a steady magnetic flux for determining the reactance of said first winding, means governed by traffic conditions of said section for controlling said circuit means whereby the voltage ofthe periodic current supplied across the traffic rails is varied in accordance with the presence or absence of a train in said section, and receiving means connected across the traffic rails of the section including an electroresponsive device effectively influenced by the periodic current. v

14. In combination with a section of railway track, a source of periodic current, a reactor having a magnetiza-ble core provided with a center and two outside magnetizable legs, means for connecting said source across the trafiic rails of the section including a first and a second winding mounted on the outside legs respectively and arranged in such a manner that magneto- V motive forces created thereby are additive, a third winding mounted on the center leg, circuit means including a source of direct current for energizing said third winding to create a steady magnetic flux for determining the reactance of said first and second windings, trafiic controlled means responsive to a train entering said section for controlling said circuit means whereby the voltage of the periodic current supplied to the trafiic rails is varied in accordance with the presence or absence of a train in said section,

a manner that magnetomotive forces created thereby are additive, a third winding mounted on the center leg of the reactor, a first means receiving periodic current from the trafilc rails of the section including the input terminals of a full-wave rectifier, means including the out- .put terminals of said rectifier for supplying unidirectional current to said third winding for controlling the permeability of the core of said reactor to govern the periodic current supplied to said trafiic rails, and a second means receiving periodic current from the traflic rails including a traflic governing electroresponsive device.

16. In combination with a section of railway track, a source of periodic current, a reactor having a magnetizable core provided with a center and two outside magnetiza-ble legs, means for connecting said source across the trafiic rails at one end of the section including a first and a second winding mounted on the outside legs respectively and arranged in such a manner that magnetomotive forces created thereby are additive, a third winding mounted on said center leg, circuit means including a source of direct current for energizing said third winding to create a steady magnetic flux for determining the reactance of said first and second windings and thereby control the periodic current, receiving means connected across the trafiic rails at the other end of the section to receive the periodic current, a traffic governing electroresponsive device controlled by said receiving means, and trafiic controlled means responsive to a train entering said section for controlling said circuit means.

BERNARD E. OHAGAN. 

